1. Field of Invention
The present invention relates to an electro-optical device, such as a liquid crystal device, and a method for manufacturing the electro-optical device, in which an electro-optical substance is sandwiched by a pair of first and second substrates bonded to each other with a sealing material at the periphery of an image display region, and the first and second substrates are provided with a pair of electrodes, respectively, disposed on the faces of the first and second substrates, each opposing the electro-optical substance.
2. Description of Related Art
Currently, an electro-optical device generally includes pixel electrodes, thin-film transistors (TFTs) for switching the pixel electrodes, a TFT-arrayed substrate which is provided with wirings, such as data lines and scan lines connected to the TFTs, for supplying image signals and scan signals, respectively, and an opposing substrate opposing a surface of the TFT-arrayed substrate provided with the wirings and the like. The opposing substrate being provided with an opposing electrode on the entire surface of the opposing substrate, other than color filters, light-shielding films, and the like.
The TFT-arrayed substrate and the opposing substrate are bonded to each other by a sealing material at a sealing region disposed around an image display region. An electro-optical substance such as liquid crystal is sandwiched by the substrates. An electrically conductive vertically-conducting material is sandwiched by the substrates at vertically conducting regions (that is, vertically conductive pads or regions at corners of the opposing substrate) provided on the respective substrates at the outside of the sealing region. A wire provided on the TFT-arrayed substrate for applying potential to an opposing electrode either to be constant or to invert at a given frequency is electrically connected to the opposing electrode via the vertically conducting material. Display is performed by driving the electro-optical substance (for example, by changes of the orientation of the liquid crystal) at a part thereof associated with each pixel electrode corresponding to a pixel by generating driving voltage between the corresponding pixel electrode and the opposing electrode.
Technologies are disclosed in, for example, Japanese Unexamined Patent Application Publication Nos. 62-89024, 11-64874, and 11-202366, in which a sealing material is provided in a sealing region which encloses a liquid crystal layer and is disposed along the four sides of a substrate and a vertically conducting material is provided in vertically conducting regions at the four comers of the substrate. Although the sealing material generally includes a non-conductive photo-curing resin or the like and the vertically conducting material includes a conductive material, the sealing material used in the sealing region and the vertically conducting material used in the vertically conductive regions include a conductive material of the same type in the technology disclosed in above Japanese Unexamined Patent Application Publication No. 62-89024. Therefore, the sealing material and the vertically conducting material can be applied in one process, whereby manufacturing processes can be simplified.
When the above electro-optical device has a large image-display region having a diagonal of, for example, approximately 20 cm or greater, bead-like or fiber-like gap-forming members for controlling a gap between substrates are spread in an electro-optical substance such as liquid crystal which is disposed in the image display region (problems do not occur because the gap-forming members are not shown as images). On the other hand, when the electro-optical device has a small image-display region having a diagonal of, for example, approximately 2 cm or smaller, the gap-forming members for controlling the gap between the substrates are generally mixed in a sealing material (so that the gap-forming members are not shown as images).
However, since the sealing material used in the technology disclosed in above Japanese Unexamined Patent Application Publication No. 62-89024 is electrically conductive, there is a drawback in that the commercialization is very difficult because short-circuiting often occurs between wirings in the sealing region. When a non-conductive sealing material is used, non-conductive gap-forming members mixed in the sealing material do not cause short-circuits between wirings even when the gap-forming members break an insulation film formed on a TFT-arrayed substrate during being bonded, and are brought into contact with the wirings. However, the gap-forming members are electrically conductive, according to the technology disclosed in the above publication, therefore, short-circuiting between the wirings occurs due to the contact of the gap-forming members.
In the technology disclosed in above Japanese Unexamined Patent Application Publication No. 11-64874, it is described that the vertically conducting material must be disposed at a given distance from an end of a substrate in order to avoid short-circuiting between upper and lower substrates. In the technology disclosed in above Japanese Unexamined Patent Application Publication No. 11-202366, wires along the periphery of an image display region to vertically conducting regions disposed at the four corners of a substrate must be provided on the substrate at the outside of the image display region in order to apply potential evenly to the entire of an opposing electrode which has a relatively high electric resistance. Therefore, according to these publications, there is a problem in that it is fundamentally difficult to reduce the sizes of the substrates or increase the size of the image display region with respect to the sizes of the substrates because the vertically conducting regions must be disposed at the outside of the sealing region.
When the size of the vertically conducting region is reduced so as to reduce the sizes of the substrates or increase the size of the image display region, vertically conductive performance becomes less reliable. When the size of the sealing region is reduced so as to reduce the sizes of the substrates or increase the size of the image display region, bonding performance and control of the gap between the substrates become less reliable.
Accordingly, it is an object of the present invention to provide an electro-optical device and a method for manufacturing an electro-optical device, in which a configuration regarding a sealing material to bond a pair of substrates to each other and a vertically conducting material between the pair of substrates can be made simple, the reliability on vertical conduction can be improved, and the sizes of the substrates can be reduced or the size of an image display region can be increased with respect to the sizes of the substrates.
To these ends, according to an aspect of the present invention, an electro-optical device can include an electro-optical substance sandwiched by a pair of a first substrate and a second substrate, a sealing material disposed between the first substrate and the second substrate for bonding the first substrate and the second substrate to each other at a sealing region along the peripheries, in plan view, of the first substrate and the second substrate, and a plurality of pixel electrodes disposed on the first substrate and in an image display region which is enclosed, in plan view, by the sealing region. The electro-optical device can further include wires provided on the first substrate and extending from the inside of the image display region to the outside of the sealing region, a vertically conducting pad disposed in the sealing region, and an opposing electrode provided on the second substrate and opposing the pixel electrodes, the opposing electrode including a vertical conductor section which opposes the vertically conducting pad. At least one part of the sealing material, which is disposed between the vertically conducting pad and the vertical conductor section, includes an electrically conductive material.
In the electro-optical device according to the present invention, an image signal and the like are supplied to the pixel electrodes via the wires formed on the first substrate. In parallel to this, an opposing-electrode-potential signal for causing potential applied to the opposing electrode formed on the second substrate, either to be constant or to invert at a given frequency, and the like are supplied via the vertically conducting pad and the vertical conductor section. Therefore, a driving voltage is applied between the image electrode and the opposing electrode at each pixel in accordance with these signals, whereby the electro-optical substance between the image electrode and the opposing electrode is driven (for example, the orientation of liquid crystal is changed by the applied driving voltage) and electro-optical image display is performed.
In this case, a portion of the sealing material including a conductive material is disposed between the vertically conducting pad and the vertical conductor section, whereby the portion of the sealing material serves as a vertical conductor, the sealing material bonding the first and second substrates to each other at the sealing region. Since a vertically conducting region can be included in the sealing region, the sizes of substrates can be reduced or the size of an image display region can be increased with respect to the sizes of the substrates compared with the above-described known technologies in which a vertically conducting region is prepared outside a sealing region and a conductive vertical conductor is provided in the vertical conducting region in addition to a sealing material. That is, since it is not necessary to prepare a vertically conducting region separately from the sealing region, the area of the sealing region can be increased, whereby the substrates can be reliably bonded to each other. The configuration of the device and a method for manufacturing the device can be made simple with at least one part of the sealing material also functioning as a vertical conductor.
A risk of disconnection or short-circuiting of the wires underlying the vertically conducting pad which is an uppermost layer on the first substrate due to the sealing material (for example, a gap-forming member included therein) can be reduced with the vertically conducting pad being provided. When the size of the vertically conducting pad in the sealing region is increased, the vertically conducting pad becomes more reliable. Therefore, the opposing electrode can be stably driven by reliable vertical conduction, whereby block ghosts in finally displayed images can be reduced.
As a result, in the electro-optical device according to the present invention, a configuration regarding the sealing material and the vertically conducting pad can be made simple, reliability on the vertical conduction and bonding between the substrates can be improved, and the sizes of the substrates can be reduced or the size of the image display region can be increased with respect to the sizes of the substrates.
In the electro-optical device according to one embodiment of the present invention, the vertically conducting pad may occupy at least one of three given sides of the sealing region. With this arrangement, the vertically conducting pad can be made much larger than the island-shaped vertically conducting pads formed at the four comers of a substrate according to the above-described known technology, because the vertically conducting pad according to the present invention occupies one, two, or three sides of the sealing region, whereby much more reliable vertical conduction can be performed, and the opposing electrode can be driven stably. When the given sides are those sides at which the wires extending from the image display region to the outside of the sealing region are not provided or which are provided with wiring structures having a relatively high mechanical strength (that is, when an electrically insulative sealing material is disposed at a side other than the given sides), a risk of disconnection or short-circuiting of the wires, which underlie the sealing material, due to the sealing material can be reduced. By forming the vertically conducting pad in units of a side of the sealing region, a gap between the substrates can be easily controlled by including a gap-forming member in the sealing material.
The vertically conducting pad may be formed at at least one of the four sides of the sealing region at which an inlet for the electro-optical substance is not formed. With this arrangement, the vertically conducting pad is provided at at least one of the sides at which an inlet for the electro-optical substance such as liquid crystal is not provided, and is not provided at the remaining sides at one of which the inlet is provided. Therefore, when an electrically insulative sealing material is disposed at the side at which the inlet is provided, a risk of disconnection or short-circuiting of the wires underlying the sealing material can be reduced. For example, when the wires are provided extending from the image display region to the outside of the sealing region at the side at which the inlet is formed, the disconnection or the short-circuit can be more advantageously reduced.
In the electro-optical device according to another embodiment of the present invention, the sealing material may include a gap-forming member mixed therein for controlling a gap between the first substrate and the second substrate. With this arrangement, the gap between the substrates can be controlled by the gap-forming member. Therefore, displayed images are prevented from deterioration due to the gap-forming member spread in an electro-optical substance of a small electro-optical device. In the electro-optical device according to the present invention, a risk of the disconnection or short-circuiting caused by the gap-forming member in the sealing region can be advantageously reduced even when the gap-forming member is mixed in the sealing material.
The gap-forming member may include electrically conductive particles at least in a portion of the sealing material disposed between the vertically conducting pad and the vertical conductor section. With this arrangement, the conductivity in the sealing member can be improved in a portion of the sealing material disposed between the vertically conducting pad and the vertical conductor section, whereby the portion of the sealing material serves as a vertical conductor.
In this case, the electrically conductive particles may be metal-plated bead-like or fiber-like particles. With this arrangement, a portion of the sealing material disposed between the vertically conducting pad and the vertical conductor section can serve as a vertical conductor with the electrically conductive particles as a conductive gap-forming member being included, the electrically conductive particles being formed of, for example, nickel-gold-plated SiO2 balls, SiO2 fibers, or the like.
According to another embodiment of the invention, at least one part of the sealing material, which is disposed between the vertically conducting pad and the vertical conductor section, may include a powdered metal mixed in the sealing material.
The conductivity in a part of the sealing material, which is disposed between the vertically conducting pad and the vertical conductor section, can be improved, whereby the part of the sealing material serves as a vertical conductor. It should be understood that the gap-forming member including electrically conductive particles described above may be mixed in the sealing material in addition to the powdered metal.
According to still another embodiment of the invention, the sealing material may include the electrically conductive material in the entire sealing region. By providing an entire sealing region serving as a vertical conductor, the configuration of the device and manufacturing processes of the device can be simplified.
According to another embodiment of the invention, the sealing material may include the electrically conductive material at least in a portion of the sealing region opposing the vertically conducting pad and include an electrically insulative material in the portion of the sealing region not opposing the vertically conducting pad. When the portion of the sealing region opposing the vertically conducting pad serves as a vertical conductor, the configuration of the device and manufacturing processes of the device can be made simple. Since the portion of the sealing material not opposing the vertically conducting pad includes an electrically insulative material, a risk of disconnection and short-circuiting of the laminated wires underlying the portion of the sealing material caused from the portion of the sealing material can be reduced.
In the electro-optical device according to another embodiment of the present invention, a surface of the vertically conducting pad formed in the sealing region may be disposed on the same plane as that of a surface of an insulation film formed in the sealing region.
The surface of the vertically conducting pad formed in the sealing region is planarized, such that the surface is disposed on the same plane as that of the surface of the insulation film formed in the sealing region, by, for example, CMP (chemical mechanical polishing) or with the vertically conducting pad being embedded in a groove formed in the substrate or an interlayer insulation layer. Therefore, the gap between the substrates can be accurately controlled when the gap is controlled by using a gap-forming member included in the sealing material disposed in the planarized sealing region.
In the electro-optical device according to still another embodiment of the present invention, a surface of the vertically conducting pad formed in the sealing region may be disposed at a level differing from the level of a surface of an insulation film formed in the sealing region, and the sealing material may include gap-forming members having diameters differing from each other in accordance with the size of a gap between the first substrate and the second substrate, the size of the gap varying between a portion of the sealing region in which the vertically conducting pad is formed and another portion of the sealing region in which the insulation film is formed so as to control the gap between the first substrate and the second substrate.
With this arrangement, since the vertically conducting pad is not planarized in the sealing region, it is difficult to accurately control the gap between the substrates according to projection and withdrawal of the vertically conducting pad when gap-forming members having a diameter the same as each other are included in the sealing material. Moreover, a risk of disconnection and short-circuiting of the wires caused by the gap-forming members in contact with the projection formed in the sealing region is increased. However, according to this embodiment of the present invention, gap-forming members, which have diameters differing from each other according to the gap between the substrates which varies between the portion of the vertically conducting pad and the portion of the insulative film, are included in the sealing material.
When the gap in the sealing region provided with the vertically conducting pad is smaller (that is, when the vertically conducting pad projects in the sealing region), the diameter of the gap-forming member disposed on the vertically conducting pad is set smaller than that of the gap-forming member which is not disposed on the vertically conducting pad. On the other hand, when the gap in the sealing region provided with the vertically conducting pad is greater (that is, when the vertically conducting pad withdraws in the sealing region), the diameter of the gap-forming member disposed on the vertically conducting pad is set greater than that of the gap-forming member which is not disposed on the vertically conducting pad. Therefore, the height of the tops of the gap-forming members disposed in the gap of which the size is not equal can become the same by varying the diameters of the gap-forming members, whereby the gap between the substrates can be accurately controlled by the gap-forming members included in the sealing material. Moreover, the risk of disconnection and short-circuiting of the wires caused by the gap-forming members in contact with the projection formed in the sealing region can be reduced.
The sealing material including the gap-forming member which has a smaller diameter corresponding to the gap of a smaller size may be disposed in a part of the sealing region associated with the gap of a larger size and in the vicinity of a boundary, at which the size of the gap varies, between the portion of the sealing region in which the vertically conducting pad is formed and the other portion of the sealing region in which the insulation film is formed.
With this arrangement, a risk in that the gap-forming member having a larger diameter moves to the side of a smaller gap from the side of a larger gap between the substrates across the boundary disposed in the sealing region at which the size of the gap varies can be reduced. That is, a risk of disconnection or short-circuiting of the wires caused by the gap-forming member having larger diameters for larger gap coming in contact with the smaller gap portion can be reduced. It is not a problem of great importance or does not present any practical problem at all that the gap-forming member having a smaller diameter moves to the side of the larger gap from the side of the smaller gap between the substrates across the boundary disposed in the sealing at which the size of the gap varies.
In the electro-optical device according to still another embodiment of the invention, the sealing material may include one of a thermosetting resin and a thermo-photo-curing resin. With this arrangement, reliable bonding between the substrates can be performed by thermo-curing the sealing material, which includes a thermosetting resin or thermo-photo-curing resin, in a manufacturing process of the electro-optical device. It is slightly difficult (although it is not impossible) to cure a sealing material including a photo-curing resin because it is slightly difficult to apply light due to interference by the vertically conducting pad which is disposed at the side of the first substrate in the sealing region. Therefore, it is advantageous to use such a sealing material including a thermosetting resin or a thermo-photo-curing resin as the sealing material according to the present invention.
According to another aspect of the present invention, a method for manufacturing an electro-optical device, by which the above-described electro-optical device according to the present invention is manufactured, can include the steps of forming the pixel electrodes, the wires, and the vertically conducting pad on the first substrate; forming the opposing electrode on the second substrate, and bonding the first substrate and the second substrate to each other with the sealing material.
In the method for manufacturing an electro-optical device, according to the present invention, the first substrate provided with the vertically conducting pad formed thereon and the second substrate provided with the opposing electrode including a vertical conductor section are bonded to each other with the sealing material, and simultaneously, a vertical conductor which vertically connects between the vertically conducting pad and the vertical conductor section can be formed with a conductive portion of the sealing material. That is, manufacturing processes can be made simple compared with a manufacturing method in which the steps of bonding of the substrates and forming the vertical conductor are individually performed. The electro-optical device according to the present invention can be relatively easily manufactured in such simplified manufacturing processes.
The method for manufacturing an electro-optical device, according to one embodiment of the present invention, may further include the step of planarizing the vertically conducting pad.
The gap between the substrates can be accurately controlled by using the sealing material including the gap-forming member disposed in the planar sealing region which is realized by, for example, performing CMP on the vertically conducting pad or embedding the same in a groove formed in the substrate or an interlayer insulation film.
In the method for manufacturing an electro-optical device, according to another embodiment of the present invention, the step of bonding with the sealing material may include the steps of applying the sealing material including a gap-forming member having a first diameter to a portion of the sealing region opposing the vertically conducting pad by using a dispenser, and applying the sealing material including another gap-forming member having a second diameter to another portion of the sealing region not opposing the vertically conducting pad by using another dispenser, the second diameter differing from the first diameter.
The sealing material including the gap-forming member which has a first diameter is applied by using one dispenser to a portion of the sealing region opposing the vertically conducting pad and the sealing material including the gap-forming member which has a second diameter is applied by using another dispenser to another portion of the sealing region not opposing the vertically conducting pad. Therefore, an electro-optical device can be relatively easily manufactured by using the method according to the present invention, in which the gap-forming members having diameters differing from each other in accordance with a projection and withdrawal of the sealing region produced due to the vertically conducting pad.
In the method for manufacturing an electro-optical device, according to still another embodiment of the present invention, the step of bonding with the sealing material may include the steps of applying the sealing material including an electrically conductive gap-forming member to a portion of the sealing region opposing the vertically conducting pad by using a dispenser, and applying the sealing material including an electrically insulative gap-forming member to another portion of the sealing region not opposing the vertically conducting pad by using another dispenser.
The sealing material including the electrically conductive gap-forming member is applied by using one dispenser to a portion of the sealing region opposing the vertically conducting pad and the sealing material including an electrically insulative gap-forming member is applied by using another dispenser to another portion of the sealing region not opposing the vertically conducting pad. Therefore, an electro-optical device can be relatively easily manufactured by using the method according to the present invention, in which vertical connection is formed with the electrically conductive gap-forming member disposed only in the portion provided with the vertically conducting pad, and disconnection or short-circuiting of the wires caused by the gap-forming member is avoided.
In the method for manufacturing an electro-optical device, according to another embodiment of the present invention, the step of bonding with the sealing material can include the step of heating the sealing material including one of a thermosetting resin and a thermo-photo-curing resin.
The substrates can be bonded to each other with heat applied to the sealing material including a thermosetting resin or a thermo-photo-curing resin. That is, the substrates can be reliably bonded to each other by the sealing material.
Although according to the present invention, it is difficult to cure a sealing material including a photo-curing resin because application of light to the sealing region at the first substrate side is difficult because of interference by the vertically conducting pad, the sealing material including a photo-curing resin may be used, in which the photo-curing resin can be cured with light applied thereto while masking an image display region, thereby avoiding deterioration of the electro-optical substance due to application of the light.
According to a further aspect of the present invention, a projection display apparatus can include a light source, a light valve including the electro-optical device according to the present invention, a light-guide member for guiding light generated by the light source to the light valve, and a projection optical element for projecting the light modulated by the light valve.
Features and further advantages of the present invention will become apparent from preferred embodiments described below.